U.S. patent application number 15/554789 was filed with the patent office on 2018-08-23 for a tool for severing or assisting in the severing of a conduit.
The applicant listed for this patent is SPEX ENGINEERING (UK) LIMITED. Invention is credited to Jamie OAG, Rae YOUNGER.
Application Number | 20180238132 15/554789 |
Document ID | / |
Family ID | 52876453 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180238132 |
Kind Code |
A1 |
OAG; Jamie ; et al. |
August 23, 2018 |
A TOOL FOR SEVERING OR ASSISTING IN THE SEVERING OF A CONDUIT
Abstract
A tool for severing or assisting in the severing of a conduit is
described. The tool comprises a housing defining a void, the void
arranged, in use, to at least partially encircle a conduit and an
at least one void access, the/each void access having an inlet and
an outlet, the/each void access inlet being in fluid communication
with the housing and the/each void access outlet being in fluid
communication with the housing void. The tool further comprises an
at least one propellant source located within the housing, an
ignition mechanism for igniting the/each propellant source and an
at least one modifying material. Upon ignition, the/each propellant
source deflagrates, creating an at least one stream of combustion
products, the/each stream of combustion products flowing out of the
tool through the/each void access in to the void, the/each void
access channelling the/each stream of combustion products towards
the conduit, the/each stream of combustion products combining with
the/each modifying material to sever or assist in severing the
conduit.
Inventors: |
OAG; Jamie; (Aberdeen,
GB) ; YOUNGER; Rae; (Aberdeenshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SPEX ENGINEERING (UK) LIMITED |
Aberdeenshire |
|
GB |
|
|
Family ID: |
52876453 |
Appl. No.: |
15/554789 |
Filed: |
March 3, 2016 |
PCT Filed: |
March 3, 2016 |
PCT NO: |
PCT/GB2016/050562 |
371 Date: |
August 31, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 33/063 20130101;
E21B 29/02 20130101 |
International
Class: |
E21B 29/02 20060101
E21B029/02; E21B 33/06 20060101 E21B033/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2015 |
GB |
1503608.0 |
Claims
1. A tool for severing or assisting in the severing of a conduit,
the tool comprising: a housing defining a void, the void arranged,
in use, to at least partially encircle a conduit; an at least one
propellant source located within the housing; an at least one void
access, the/each void access having an inlet and an outlet,
the/each void access inlet being in fluid communication with the
housing and the/each void access outlet being in fluid
communication with the housing void; an ignition mechanism for
igniting the/each propellant source; and an at least one modifying
material; wherein, upon ignition, the/each propellant source
deflagrates, creating an at least one stream of combustion
products, the/each stream of combustion products flowing out of the
tool through the/each void access in to the void, the/each void
access channelling the/each stream of combustion products towards
the conduit, the/each stream of combustion products combining with
the/each modifying material to sever or assist in severing the
conduit.
2. A tool according to claim 1, wherein the housing void is a
housing throughbore, the housing throughbore, in use, encircling a
conduit.
3. A tool according to claim 1, wherein the/each stream of
combustion products heats the conduit, in some cases to a
temperature sufficient to soften the conduit, and the modifying
material impinges on at least a portion of the conduit,
transferring energy to the conduit to be manipulated, thereby
forcibly displacing or moving the conduit portion.
4. A tool according to claim 1, wherein there are a plurality of
void accesses.
5. A tool according to claim 4, wherein, where there is a plurality
of void accesses, the void accesses are arranged in an array.
6. A tool according to claim 5, wherein each void access in any
given array of void accesses has a focal point the same distance
from the void longitudinal axis as every other void access in the
same array.
7. A tool according to claim 1, wherein a stream of combustion
products and modifying material flows through each void access or
array of void accesses in a sequence.
8. A tool according to claim 1, wherein the/each void access is
defined by a housing wall.
9. A tool according to claim 8, wherein the/each void access is an
aperture in the housing wall, the/each aperture having a
sidewall.
10. A tool according to claim 9, wherein the aperture sidewall
channels the stream of combustion products and/or the/each
modifying material.
11. A tool according to claim 1, wherein the tool includes an at
least one carrier, the/each void access being mounted to the/each
carrier.
12. A tool according to claim 11, wherein the/each carrier is
movable between a retracted position and a deployed position.
13. A tool according to claim 12, wherein in the deployed position
the/each carrier is adjacent to the conduit.
14. A tool according to claim 11, wherein the carrier comprises
rams movable in a plane perpendicular to a tool longitudinal
axis.
15. A tool according to claim 11, wherein the carrier comprises
rollers configured to rotate into engagement with the conduit.
16. A tool according to claim 15, wherein the rollers defines a
recess for receiving the conduit.
17. A tool according to claim 1, wherein the or at least one of the
modifying materials includes solid particles.
18. A tool according to claim 1, wherein the or at least one of the
modifying materials contain liquid droplets.
19. A tool according to claim 1, wherein the or at least one of the
modifying materials is included within the propellant source.
20. A tool according to claim 1, wherein the or at least one of the
modifying materials is a metal.
21. A tool according to claim 20, wherein the metal at least
partially melts as the/each propellant source deflagrates.
22. A tool according to claim 20, wherein the metal at least
partially oxidises.
23. A tool according to claim 1, wherein the or at least one of the
modifying materials is formed by the at least partial deflagration
of the/each propellant source.
24. A tool according to claim 1, wherein the or at least one of the
modifying materials is formed separately from the deflagration of
the/each propellant source.
25. A tool according to claim 1, wherein the or at least one of the
modifying materials is present in the tool prior to ignition of
the/each propellant source.
26. A tool according to claim 1, wherein the or at least one of the
modifying materials is introduced into the/each stream of
combustion products.
27. A tool according to claim 1, wherein the or at least one of the
modifying materials is mechanically or forcibly introduced into the
propellant gas and/or the/each stream of combustion products.
28. A tool according to claim 1, wherein the tool includes a
positioning mechanism for positioning a conduit, in use, with
respect to the/each void access.
29. A tool according to claim 28, wherein the positioning mechanism
centres the conduit with respect to the void.
30. A tool according to claim 28, wherein the positioning mechanism
comprises a plurality of positioning devices, each device being
configured to engage the conduit.
31. A tool according to claim 28, wherein the positioning mechanism
centres the conduit with respect to the longitudinal void axis.
32. A tool according to claim 1, wherein the/each void access is
movable with respect to the conduit to a position where the
severing action of the/each stream of combustion products and
modifying material is optimised.
33. A tool according to claim 1, wherein the tool is configured,
within a fluid filled environment, to locally purge the medium
between the void accesses and the conduit, and replace this medium
with a medium of lower density or a fluid with beneficial
effects.
34. A tool according to claim 33, wherein the medium of lower
density is a gas.
35. A tool according to claim 34, wherein the tool produces the gas
through propellant deflagration.
36. A tool according to claim 34, wherein the gas is used to
displace the fluid in the vicinity of the tool.
37. A tool according to claim 1, wherein the tool further includes
a sealing mechanism.
38. A tool according to claim 37, wherein the sealing mechanism is
adapted to form a seal to isolate a section of the conduit.
39. A tool according to claim 37, wherein the sealing mechanism is
a packer or sealing element above and/or below the housing.
40. A tool according to claim 1, wherein the tool comprises a
restraining or fastening mechanism to restrict relative movement
between the tool and the conduit.
41. A tool according to claim 40, wherein the restraining or
fastening mechanism forms a seal on the conduit to assist in, at
least partially, confining the stream of combustion products and
modifying material to a stationary conduit location.
42. A tool according to claim 1, wherein the tool is configured to
impart additional forces onto the conduit.
43. A tool according to claim 42, wherein the tool applies torsion,
tension or bending to the conduit.
44. A tool according to claim 43, wherein the at least one stream
of combustion products and/or the/each modifying material applies
torsion or tension or bending to the conduit.
45. A tool according to claim 1, wherein the tool is configured to
rotate the/each stream of combustion products in a vortex.
46. A tool according to claim 1, wherein the tool comprises a
shearing mechanism configured to seal a wellbore.
47. A tool according to claim 1, wherein the tool comprises a
scraping mechanism to scrape away molten or softened conduit
material.
48. A tool according to claim 1, wherein there is a plurality of
propellant sources.
49. A tool according to claim 48, wherein where there is the
plurality of propellant sources, each propellant source deflagrates
separately.
50. A tool according to claim 49, wherein where there is the
plurality of propellant sources, at least some of the propellant
sources are ignited in a sequence.
51. A tool according to claim 1, wherein the/each propellant source
and, in some embodiments the associated ignition mechanism, is
thermally insulated from well temperatures and/or potentially high
temperatures from the stream of combustion products and/or
modifying material.
52. A tool according to claim 1, wherein additional energy can be
imparted to the/each stream of combustion products and/or the each
modifying material by ionisation.
53. A tool according to claim 52, wherein the/each stream of
combustion products and/or the/each modifying material is at least
partially ionised by at least part of the/each stream of combustion
products and/or the/each modifying material coming into contact
with an electrical arc.
54. A tool according to claim 52, wherein the/each stream of
combustion products and/or the/each modifying material is ionised
by passing through an induction coil.
55. A tool according to claim 52, wherein additional energy can be
imparted to the/each stream of combustion products and/or the/each
modifying material by passing at least a portion through a magnetic
field and/or electric field.
56. A tool according to claim 52, wherein additional energy can be
imparted to the/each stream of combustion products and/or the/each
modifying material by passing at least a portion through microwave
radiation.
57. A tool according to claim 52, wherein additional energy can be
imparted to the/each stream of combustion products and/or the/each
modifying material by raising its temperature.
58. A method of severing or assisting in the severing of a conduit,
the method comprising the steps of: providing a tool having a
housing, the housing defining a void, the void at least partially
encircling a conduit to be severed; igniting an at least one
propellant source located within the housing, the/each propellant
source upon deflagration creates an at least one stream of
combustion products, the/each stream of combustion products flowing
out of the tool through an at least one void access, the/each void
access channelling the/each stream of combustion products towards
the conduit, the/each stream of combustion products containing
and/or combining with at least one modifying material to sever or
assist in severing the conduit.
Description
FIELD
[0001] The present invention relates to a tool for severing or
assisting in the severing of a target. In some embodiments, the
present invention relates to a tool for severing or assisting in
the severing of a conduit in a hydrocarbon extraction well at a
location above the in-situ well completion.
BACKGROUND
[0002] During hydrocarbon extraction operations, safety equipment
is installed for utilisation in the event of catastrophic failure
to prevent damage to human life, the environment, assets (tangible
and intangible) and also prevent wider societal impacts. This is
particularly the case for subsea hydrocarbon extraction where the
presence of water can carry contamination from an oil well many
thousands of miles, potentially causing huge environmental
damage.
[0003] During drilling operations and some well intervention
operations, the primary barrier utilised to shut a well is the blow
out preventer (BOP), which sits on the wellhead. For a subsea well,
a riser links the oil rig to the BOP, the riser allowing the
passage of drilling equipment, drilling tools, completion equipment
and completion tools, particularly conduits such as wellbore
tubulars, from the oil rig into the oil well through the BOP. In
the event of a major well control event, it is beneficial to be
able to sever conduits such as tubulars, including drill pipe and
the like, within the riser to, first, permit successful detachment
of the rig from the well head and, second, allow the severed
conduit to move out of the way from the closure mechanism of the
BOP, allowing the blow out preventer to close more easily.
[0004] The Deepwater Horizon/Macondo well blowout and explosion
incident on 10th April 2010 highlighted a number of technical
deficiencies in well control equipment used at the time and which
are still in use today. A key issue highlighted was that BOPs, in
use, had major limitations in terms of being able to successfully
isolate the BOP in a major well control incident when there were
`non-shearable` items such as large diameter casing, drill pipe or
a drill collar across the BOP. Furthermore, BOPs were designed for
severing centralised shearable items across the BOP and not
non-centralised shearable items, that may also be under `effective
compression`.
SUMMARY
[0005] According to a first aspect of the present invention there
is provided a tool for severing or assisting in the severing of a
conduit, the tool comprising:
[0006] a housing defining a void, the void arranged, in use, to at
least partially encircle a conduit;
[0007] an at least one propellant source located within the
housing;
[0008] an at least one void access, the/each void access having an
inlet and an outlet, the/each void access inlet being in fluid
communication with the housing and the/each void access outlet
being in fluid communication with the housing void;
[0009] an ignition mechanism for igniting the/each propellant
source; and
[0010] an at least one modifying material;
[0011] wherein, upon ignition, the/each propellant source
deflagrates, creating an at least one stream of combustion
products, the/each stream of combustion products flowing out of the
tool through the/each void access in to the void, the/each void
access channelling the/each stream of combustion products towards
the conduit, the/each stream of combustion products combining with
the/each modifying material to sever or assist in severing the
conduit.
[0012] A propellant is an explosive material which has a low rate
of combustion and once ignited deflagrates (burns) or otherwise
decomposes to produce propellant gas. This gas when confined is
pressurised, the pressure driving the gas and other combustion
products away from the propellant, forming a stream of combustion
products. A propellant can deflagrate smoothly and at a uniform
rate after ignition without depending on interaction with the
atmosphere, and produces propellant gas and/or heat on combustion
and may also produce additional combustion products.
[0013] In the preferred embodiments, by "conduit" it is meant any
object that is run into a wellbore or forms part of an oil and gas
wellbore completion or well drill string or well intervention
system, whether hollow, like a tubular, or solid like a wellbore
drift. "Conduit" includes, but is not limited to, braided wire,
coiled tubing, drill pipe, production tubing, casing, riser, well
intervention tools and well completion tools. Conduits may be
cylindrical or non-cylindrical.
[0014] In at least one embodiment of the invention a tool is
provided which uses a stream of combustion products created by
combustion of a propellant source combined with a modifying
material to sever or assist in severing a conduit. This is achieved
by processes such as ablation, severing, displacement, removal,
heating, abrasion, or erosion.
[0015] The combination of a stream of combustion products propelled
towards the conduit at high pressure and a modifying material, will
manipulate the conduit causing severance, or at least change the
physical properties, of a section of the conduit to permit other
conventional tools, such as blowout preventer shear rams, to
complete severance.
[0016] The housing void may be a housing throughbore, the housing
throughbore, in use, encircling a conduit.
[0017] The tool may be configured to be used above a cased
wellbore.
[0018] In use, the/each stream of combustion products may heat the
conduit, in some cases to a temperature sufficient to soften the
conduit, and the modifying material may impinge on at least a
portion of the conduit, transferring energy to the conduit to be
manipulated, thereby forcibly displacing or moving the conduit
portion.
[0019] The/each void access may be channelled towards a focal
point. The focal point of a void access is where the stream of
combustion products from that void access is most intense.
[0020] At least one void access may be fixed relative to the
housing.
[0021] Alternatively or additionally, at least one void access may
be movable with respect to the housing.
[0022] Where the void is a throughbore, the at least one void
access may provide circumferential access to the housing void.
Either one circumferential void access or multiple void accesses
can be provided to enable the stream of combustion products and
modifying material to have 360.degree. access to the void.
[0023] In a preferred embodiment there may be a plurality of void
accesses.
[0024] Where there is a plurality of void accesses, the void
accesses may be arranged in an array.
[0025] The array may be a linear array.
[0026] The array may be a tiered array.
[0027] A first array of void accesses or a first tier of an array
of void accesses may lie on a first plane, the first plane being
substantially perpendicular to a longitudinal axis of the void.
[0028] Second and subsequent arrays of void accesses or second
subsequent tiers of void accesses may lie in second and subsequent
planes respectively, perpendicular to the longitudinal axis of the
void.
[0029] Each void access in any given array of void accesses may
have a focal point the same distance from the void longitudinal
axis as every other void access in the same array.
[0030] Each void access in one array may have a focal point at a
different distance from the void longitudinal axis as every other
void access in another array.
[0031] A stream of combustion products and modifying material may
flow through each void access or array of void accesses in a
sequence. Such an arrangement permits the focus of the streams of
combustion products to move, for example, towards the void
longitudinal axis as the arrays are utilised. In one embodiment,
where there are arrays of void accesses, the first array is focused
on the surface of the conduit to be manipulated and the
subsequently utilised second array is focused 10 mm to 15 mm, for
example, to the tool longitudinal axis. In this way, the stream of
combustion products and modifying material passing through the
first array penetrates the outer surface of the conduit. Once the
maximum effectiveness of this stream of combustion products and
modifying material has peaked, a stream of combustion products and
modifying material passes through the second array which is focused
slightly further into the conduit, maintaining the efficiency of
the severing process. This transfer of flow could be achieved by,
for example, the second array having a separate propellant source
which is triggered later than the propellant source associated with
the first array, or there could be relative movement between the
propellant source and the void access arrays such that the
alignment of the propellant source moves from the first array of
void accesses to the second array of void accesses.
[0032] At least one void access may share a focal point with at
least one other void access. Such an arrangement allows multiple
streams of combustion products and modifying material to converge
on, for example, a point on the surface of the conduit.
[0033] The/each void access may be defined by a housing wall.
[0034] The/each void access may be an aperture in the housing wall,
the/each aperture having a sidewall.
[0035] The aperture sidewall may channel the stream of combustion
products and/or the/each modifying material.
[0036] The tool may include an at least one carrier, the/each void
access being mounted to the/each carrier.
[0037] The/each carrier may be movable between a retracted position
and a deployed position.
[0038] In the retracted position, the/each carrier may be clear of
the void, and in the deployed position the/each carrier may
encroach the void.
[0039] In the deployed position the/each carrier may be adjacent to
the conduit. Bringing the void accesses into the proximity of the
conduit gives a greater chance of successful operation of the tool
as it minimises the distance that the/each stream of combustion
products and modifying material has to travel.
[0040] The carrier may comprise rams movable in a plane
perpendicular to the tool void.
[0041] The carrier may comprise rollers configured to rotate into
engagement with the conduit.
[0042] The rollers may define a recess for receiving the
conduit.
[0043] In at least one embodiment of the present invention the or
at least one of the modifying materials may include solid
particles. Solid particles can cause abrasion of the material to be
manipulated.
[0044] Alternatively or additionally the or at least one of the
modifying materials may include liquid droplets. Liquid droplets
can cause erosion of the material to be manipulated and be a very
good thermal transfer mechanism.
[0045] The or at least one of the modifying materials may be
contained within the propellant source.
[0046] The or at least one of the modifying materials may be a
metal.
[0047] The metal may at least partially melt as the/each propellant
source deflagrates.
[0048] In other embodiments, the or at least one of the modifying
materials may have been substantially solid, for example
garnet.
[0049] In some embodiments, the metal may, additionally or
alternatively, at least partially oxidise.
[0050] The or at least one of the modifying materials may be formed
by the at least partial deflagration of the/each propellant
source.
[0051] Alternatively or additionally, the or at least one of the
modifying materials may be formed separately from the deflagration
of the/each propellant source.
[0052] Alternatively or additionally, the or at least one of the
modifying materials may be present in the tool prior to ignition of
the/each propellant source.
[0053] In at least one embodiment the or at least one of the
modifying materials may be introduced into the/each stream of
combustion products.
[0054] In at least one embodiment the or at least one of the
modifying materials may be mechanically or forcibly introduced into
the propellant gas and/or the/each stream of combustion
products.
[0055] The tool may include an at least one sacrificial
portion.
[0056] The/each sacrificial portion may comprise the or at least
one of the modifying materials.
[0057] In at least one embodiment, the/each stream of combustion
products may erode the sacrificial housing portion, erosion of the
sacrificial housing portion releasing at least one modifying
material into the/each stream of combustion products.
[0058] The/each sacrificial portion may form part of the sidewall
of the/each void access.
[0059] Alternatively or additionally, where the void access
sidewall includes a sacrificial portion, erosion of the sacrificial
portion may change the focal point of the void access.
[0060] The tool may include a positioning mechanism for positioning
a conduit, in use, with respect to the/each void access.
[0061] The positioning mechanism may centre the conduit with
respect to the void. Positioning the conduit in a known location
ensures a consistency of performance of the tool.
[0062] The positioning mechanism may comprise a plurality of
positioning devices, each device being configured to engage the
conduit.
[0063] The positioning mechanism may centre the conduit with
respect to the longitudinal void axis.
[0064] In alternative embodiments, the/each void access may be
movable with respect to the conduit to a position where the
severing action of the/each stream of combustion products and
modifying material is optimised. In this embodiment, the/each void
access move towards the conduit rather than the conduit being
positioned adjacent to the/each void access.
[0065] The tool may be configured, within a fluid filled
environment, to locally purge the medium between the void accesses
and the conduit, and replace this medium with a medium of lower
density or a fluid with beneficial effects. It is desirable to
remove well fluids from the section and/or to reduce pressure
within the section to maximise the severing of the tool on the
conduit. Fluids and solids, in particular, within the wellbore can
provide an extremely dense medium through which the stream of
combustion products and modifying material have to pass. This can
significantly reduce the energy of the/each stream of combustion
products and modifying material have an adverse effect on their
ability to sever or assist in severing the conduit. By purging, for
example, a fluid in the wellbore and replacing the fluid with a
lower density gas, the tool then produces a stream of combustion
products within a gaseous environment, thereby reducing the energy
lost during the passage of the stream of combustion products and
modifying material to the conduit.
[0066] The medium of lower density may be a gas.
[0067] The tool may produce the gas through propellant
combustion.
[0068] The gas may be used to displace the fluid in the vicinity of
the tool.
[0069] In some embodiments, the gas may flow through the void
accesses and, is utilised to channel the stream of combustion gases
and additional material towards the conduit.
[0070] The tool may further include a sealing mechanism.
[0071] The sealing mechanism may be adapted to form a seal to
isolate a section of the conduit. In one embodiment the use of two
or more seals may be desirable to isolate the section of the
conduit to be severed.
[0072] In at least one embodiment of the present invention, the
sealing mechanism is a packer or sealing element above and/or below
the housing.
[0073] The tool may comprise a restraining or fastening mechanism.
In at least one embodiment of the present invention the tool
restrains the conduit while the stream of combustion products and
modifying material severs or assists in severing the conduit. This
would allow more time for the stream of combustion products and
modifying material to interact with the conduit at a single
stationary target location.
[0074] The restraining or fastening mechanism may form a seal on
the conduit to assist in, at least partially, confining the stream
of combustion products and modifying material to a stationary
conduit location.
[0075] The tool may be configured to impart additional forces onto
the conduit. In at least one embodiment of the present invention
these forces are beneficial in assisting the stream of combustion
products and modifying material in interacting with the conduit and
severing the conduit.
[0076] In at least one embodiment of the present invention the tool
imparts additional forces which move the conduit, to expose the
conduit to the stream of combustion products and modifying
material.
[0077] The tool may move the conduit by, for example, rotation.
[0078] Alternatively or additionally the tool may apply torsion,
tension or bending to the conduit. These additional forces may
assist in conduit penetration, displacement and/or severance.
[0079] The at least one stream of combustion products and/or
the/each modifying material may apply torsion or tension or bending
to the conduit.
[0080] The tool may be configured to move the streams of combustion
products such that they impinge at a pre-determined position on a
moving conduit. The movement may be driven mechanically,
electrically or magnetically. In some embodiments the propellant
combustion products' reaction force and/or propellant by-products
drive the movement.
[0081] The tool may be configured to move the streams of combustion
products in a single direction.
[0082] The tool may be configured to rotate the/each stream of
combustion products and modifying material around the conduit.
[0083] The tool may be configured to rotate the/each stream of
combustion products in a vortex. By utilising vortices, adjacent
streams can interact to combine or push apart.
[0084] The tool may further comprise a shearing mechanism.
[0085] The shearing mechanism may be a mechanical shearing
mechanism.
[0086] The shearing mechanism may be configured to be driven by
propellant combustion gases.
[0087] The shearing mechanism may be configured to act at or next
to the location where the stream of combustion products and
modifying material are directed.
[0088] The tool may further comprise a scraping mechanism to scrape
away molten or softened conduit material.
[0089] There may be a plurality of propellant sources.
[0090] Where there is the plurality of propellant sources, each
propellant source may combust separately.
[0091] Where there is the plurality of propellant sources, at least
some of the propellant sources may be ignited in a sequence.
[0092] At least one of the propellant sources may be used as a
structural component on or within the tool.
[0093] In at least one embodiment of the present invention, a
portion of the structure of the tool is made from propellant which
deflagrates when the tool operates, leaving minimal debris to
recover.
[0094] The/each propellant source and, in some embodiments the
associated ignition mechanism, may be thermally insulated from well
temperatures and/or potentially high temperatures from the stream
of combustion products and/or modifying material. Thermally
insulating the propellant sources (the associated ignition
mechanism) can prevent thermal degradation, and a possible
reduction in performance, of the propellant sources and, in some
cases the associated ignition mechanism. In other embodiments or in
the same embodiments, the/each propellant sources and, in some
embodiments the associated ignition mechanism, may be shielded from
well pressure.
[0095] In some embodiments the at least one modifying material may
be thermally insulated.
[0096] In some embodiments, additional energy can be imparted to
the/each stream of combustion products and/or the each modifying
material by ionisation.
[0097] The/each stream of combustion products and/or the/each
modifying material may be at least partially ionised by at least
part of the/each stream of combustion products and/or the/each
modifying material coming into contact with an electrical arc.
[0098] The/each stream of combustion products and/or the/each
modifying material may be ionised by passing through an induction
coil.
[0099] In some embodiments, additional energy can be imparted to
the/each stream of combustion products and/or the/each modifying
material by passing at least a portion through a magnetic field
and/or electric field.
[0100] In some embodiments, additional energy can be imparted to
the/each stream of combustion products and/or the/each modifying
material by passing at least a portion through microwave
radiation.
[0101] In some embodiments, additional energy can be imparted to
the/each stream of combustion products and/or the/each modifying
material by raising its temperature.
[0102] In some embodiments, additional energy increases the volume
and/or temperature and/or pressure of the/each stream of combustion
products and/or the/each modifying material and excites the
molecules.
[0103] Additional energy can be imparted to the/each stream of
combustion products and/or the/each modifying material in the/each
void access.
[0104] Alternatively, additional energy can be imparted to the/each
stream of combustion products and/or the/each modifying material
outside the/each void access.
[0105] According to a second aspect of the present invention there
is provided a method of severing or assisting in the severing of a
conduit, the method comprising the steps of:
[0106] providing a tool having a housing, the housing defining a
void, the void at least partially encircling a conduit to be
severed;
[0107] igniting an at least one propellant source located within
the housing, the/each propellant source upon deflagration creates
an at least one stream of combustion products, the/each stream of
combustion products flowing out of the tool through an at least one
void access, the/each void access channelling the/each stream of
combustion products towards the conduit, the/each stream of
combustion products combining with at least one modifying material
to sever or assist in severing the conduit.
[0108] According to a third aspect of the present invention there
is provided a severance tool for severing a target, the severance
tool comprising:
[0109] a housing;
[0110] at least one chamber for housing a propellant source;
[0111] at least one nozzle, the/each nozzle having an inlet and an
outlet, the/each inlet being in fluid communication with at least
one chamber; and
[0112] at least one mechanism for igniting the/each propellant
source;
[0113] wherein, upon ignition, at least one of the propellant
sources combusts to release combustion gas in the form of at least
one combustion jet, which, in use, flows out of the severance tool
through the/each nozzle outlet towards the target.
[0114] The target may be a conduit.
[0115] Some or all of the propellant may comprise a solid.
[0116] Preferably, some or all of the propellant may comprise a
liquid.
[0117] The composition of the propellant source may be adjusted to
change the combustion temperature, the quantity of gas produced,
the by-products produced and any similar desirable feature.
[0118] The combusting area of the propellant source may be
configured to achieve a desired combustion rate. The geometry of
solid propellant may be adjusted to decrease or increase the
propellant combustion rate. This may be achieved by modifying the
surface area which combusts (for example a star-shaped
cross-section will deflagrate faster than an equivalent size of
solid cylindrical propellant). The propellant combustion rate may
remain constant or may increase or reduce during operation.
[0119] In at least one embodiment, the/each combustion jet may be a
stream of combustion products.
[0120] In at least one embodiment, the/each combustion jet may
comprise one or more of propellant gas, heat and/or combustion
products.
[0121] In at least one embodiment the propellant source(s) may
combust continuously.
[0122] The propellant source(s) may combust intermittently.
[0123] The/each combustion jet may be continuous. Alternatively
the/each combustion jet may be intermittent.
[0124] The/each combustion jet may be circumferential, radially
focussed inwards. The/each combustion jet may share a single common
focus or may be directed at different locations on the target.
The/each combustion jet may be stationary in operation. The/each
combustion jet may move or have active/passive control.
[0125] In some embodiments, the/each combustion jet may be biased
to a particular direction.
[0126] In some embodiments, when directed through a nozzle,
the/each combustion jet can be accelerated.
[0127] The/each combustion jet may be accelerated by imparting
additional energy to the/each combustion jet.
[0128] Alternatively or additionally, the/each combustion jet may
be raised in temperature by imparting additional energy to the/each
combustion jet.
[0129] The propellant sources may be a single state, a solid,
liquid or gas or may be in two or more states.
[0130] Alternatively the propellant sources may be in separate
states, which are combined at or prior to combustion
initiation.
[0131] Alternatively or additionally the propellant sources may
change state prior to ignition.
[0132] There may be a plurality of propellant sources.
[0133] Where there is a plurality of propellant sources, each
propellant source may combust separately.
[0134] In this embodiment, one propellant source may be separated
from an adjacent propellant source by means of a barrier.
[0135] The barrier may comprise a non-combustible layer.
[0136] The barrier may comprise a void.
[0137] The void may be defined by adjacent propellant sources.
[0138] Where there is a plurality of propellant sources, at least
some of the propellant sources may be ignited in a sequence, or
alternatively, substantially simultaneously.
[0139] Where there is a plurality of propellant sources, at least
some of the propellant sources may be equidistant from a nozzle
inlet, or alternatively, arranged at varying distances from a
nozzle inlet.
[0140] Where there is a plurality of propellant sources, at least
some of the propellant sources may be associated with its own
nozzle inlet, or alternatively, share a nozzle inlet.
[0141] The tool may comprise at least one source of additional
material.
[0142] The additional material may be a modifying material, adapted
to manipulate the target by, for example, ablation, severing,
shearing, displacement, removal, heating, abrasion, or erosion.
[0143] The/each additional material source may be solid, liquid
and/or gas or any combination thereof.
[0144] In at least one embodiment of the tool the/each combustion
jet and/or additional materials may be generated within the tool
without generating heat or with minimal heat generation. Certain
types of propellant can combust without generating heat. The
propellant gas, combustion products and/or additional materials
interact with the target, and the risk of igniting flammable
materials that may be present or in close proximity is reduced or
eliminated.
[0145] There may be a plurality of combustion jets.
[0146] In at least one embodiment of the present invention the/each
nozzle outlets projects a combustion jet, comprising propellant
gas, combustion products and/or additional materials.
[0147] In at least one embodiment of the present invention the/each
nozzle directs or biases the/each combustion jet in a particular
direction. The/each nozzle can include a venturi or de laval or
similar geometry to expand and/or accelerate the/each combustion
jet, which imparts greater speed and/or kinetic energy to the
ejected media from the tool.
[0148] Additionally the/each nozzle imparts a desired shape to
the/each combustion jet which is ejected from the tool.
[0149] At least one of the/each combustion jet may be linear.
[0150] At least one of the/each combustion jet may be
circumferential.
[0151] At least one of the/each nozzle may impart a rotation to
the/each combustion jet.
[0152] At least one of the/each nozzle may bifurcate the/each
combustion jet into two or more combustion jets.
[0153] At least one of the/each nozzle may comprise a screen with a
plurality of holes for creating a plurality of combustion jets.
[0154] At least a portion of at least one nozzle may point
obliquely inwards from the tool housing.
[0155] At least a portion of at least one nozzle may point
perpendicularly inwards from the tool housing.
[0156] At least a portion of each of a plurality of nozzles may
point in convergent directions.
[0157] In at least one embodiment of the present invention
convergent nozzles create a combustion jet that has greater
penetration than the/each combustion jet created by a single
nozzle.
[0158] At least some of the/each nozzle may point in convergent
directions and their respective combustion jets converge at the
target surface.
[0159] At least some of the/each adjacent nozzle may point in
convergent directions and their respective combustion jets converge
before reaching the target surface.
[0160] A thrust/reaction force from a nozzle may be used to move
the tool.
[0161] The thrust/reaction force from a nozzle may be used to bring
the tool into closer proximity to the target.
[0162] The thrust/reaction force from a nozzle may be used to move
components within the tool.
[0163] In at least one embodiment of the present invention the
thrust from the tool moves the nozzle in a circular path to remove
circular sections from the target.
[0164] The pressure generated by the combustion process may be used
to move the tool.
[0165] The pressure generated by the combustion process may be used
to bring the tool into closer proximity to the target.
[0166] The pressure generated by the combustion process may be used
to move components within the tool.
[0167] The combustion chamber within the tool may maintain a
constant volume.
[0168] In at least one embodiment of the present invention the
pressure generated by the combustion process moves the propellant
within the tool to maintain a constant volume combustion
chamber.
[0169] The tool may comprise an air source to combust the
propellant.
[0170] At least one of the/each mechanism for igniting the
propellant may comprise an electro-pyrotechnic igniter.
Electro-pyrotechnic igniters are controlled electrically, for
example with a heated bridgewire or a bridge resistor.
[0171] In at least one embodiment of the present invention an
electro-pyrotechnic igniter may be safer to operate than a purely
pyrotechnic igniter or series of instantaneous igniters
[0172] At least one of the/each mechanism for igniting the
propellant may comprise a pyrogen.
[0173] The pyrogen may comprise a pyrotechnic composition made of a
fuel and an oxidiser. In use, the fuel produces a significant
amount of hot particles that cause or promote the ignition of the
propellant.
[0174] At least one of the/each mechanism for igniting the
propellant may comprise an electrical igniter. In at least one
embodiment of the present invention an electrical igniter is safer
to operate and handle than a pyrotechnic igniter.
[0175] Optionally the electrical igniter may comprise a
bridgewire.
[0176] Alternatively or additionally the electrical igniter may be
adapted to create a spark.
[0177] At least one of the/each mechanism for igniting the
propellant may comprise a chemical igniter.
[0178] In this embodiment, at least one nozzle may be aligned such
that the/each combustion jet generated on combustion of the
propellant source travels in a direction which is non-perpendicular
to the target surface.
[0179] A plurality of nozzles may be aligned such that the/each
combustion jets generated on combustion of the propellant source
travel in a direction which is non-perpendicular to the target
surface.
[0180] At least one nozzle may be aligned such that the/each
combustion jet released upon propellant source combustion is
directed, in use, at the target longitudinal axis.
[0181] Additionally or alternatively, where the target is a tubular
element, at least one nozzle may be aligned such that the/each
combustion jet released upon combustion of the propellant source is
directed at a tangent to a target internal surface.
[0182] In some embodiments, at least one nozzle is aligned such
that the/each combustion jet released upon combustion of the
propellant source is directed at a trajectory such that the energy
of the/each combustion jet is dissipated within the material from
which the target is made.
[0183] In some embodiments, at least one nozzle is aligned such
that the/each combustion jet released upon combustion of the
propellant source is directed at a trajectory such that the energy
of the/each combustion jet is dissipated at or adjacent to the
target internal surface.
[0184] In some embodiments, where the target is tubular, at least
some of the nozzles may be aligned such that the/each combustion
jet released by combustion of the propellant source is directed at
a tangent to the target internal surface. By directing the/each
combustion jets released upon combustion of the propellant source
tangentially to the target internal surface, the distance the/each
combustion jet travels through the target is maximised thereby
maximising the damage caused by the/each combustion jet on the
target material.
[0185] The nozzles may be aligned such that the/each combustion jet
released upon combustion of the propellant source cooperates with
the/each combustion jet released by another nozzle to create
separation forces and/or cavities within the target.
[0186] In some embodiments, the nozzles may be grouped and aligned
such that the/each combustion jets released upon combustion of the
propellant source of one group of nozzles cooperate with the/each
combustion jets released by another group of nozzles to create
separation forces and/or cavities within the target.
[0187] The tool may comprise at least one outlet for evacuating or
venting the combustion products generated by the combustion of the
propellant source(s). The at least one outlet may comprise a
bleeding bore used to vent gas. Alternatively or additionally, the
outlet may comprise a pressure relief member.
[0188] The outlet for evacuating or venting the combustion gases
may be configured to send a shockwave downhole for attenuating a
pressure surge.
[0189] The tool may comprise a protecting sleeve for protecting the
propellant source(s) from the tool environment.
[0190] The outlet for evacuating or venting the combustion gases
may be configured to move the protecting sleeve.
[0191] The at least one chamber for housing a propellant source may
be movable with respect to the tool housing.
[0192] The tool may comprise a combustion chamber for carrying out
the combustion of the propellant source.
[0193] The tool may comprise flanges for connecting the tool to
other well equipment.
[0194] The tool may comprise one or more linear shaped charges.
[0195] The tool may comprise at least one ram wherein such rams are
configured to eject at least one combustion jet. In at least one
embodiment of the present invention a pair of rams debilitate the
target material by ejecting combustion jets from the front of the
rams and subsequently sever the target by applying compression
forces with the rams.
[0196] The at least one ram may be at least partially driven by
combustion products from the propellant source combustion.
[0197] The tool may be used to supplement and enhance other
conventional target severing methods. In at least one embodiment of
the present invention the tool releases combustion jets to
debilitate or soften the target which is cooperatively severed by
linear shaped explosive charges.
[0198] The at least one chamber for housing the propellant source
may be configured to resist oilwell pressures externally.
[0199] The present invention can be used to sever targets
independently of the environmental pressure. It can be used on the
surface but it can also be used at high pressures, such as those
found in oilwell environments. It is understood that high
environmental pressures favour the combustion of the propellant
source and produce a more consistent severance, due to the fact
that the/each combustion jet is more focused due to pressure, i.e.
it is less dispersed.
[0200] The tool may be configured to create, in use, a gas bubble
from the combustion gas between the nozzles and the target.
[0201] The tool may comprise a sacrificial portion mounted on a
target for facilitating severance of the target.
[0202] The sacrificial portion may be clamped on the target.
[0203] The sacrificial portion may be a part mechanically weaker
than the rest of the target.
[0204] The sacrificial portion may comprise a part with a lower
melting point than the rest of the target.
[0205] The sacrificial portion may comprise a part which is
mechanically weaker and with a lower melting point than the rest of
the target.
[0206] In one embodiment, the sacrificial portion comprises a
reinforced composite material able to withstand the same mechanical
stresses as the rest of the target (such as a drillstring), the
composite matrix being of a substantially lower melting point than
the target material, such that, in an emergency event, the
propellant jet is used to rapidly soften the composite matrix and
the tool is able to rapidly and efficiently sever the target.
[0207] The tool may comprise a tracking system configured to track
the position of the target relative to the tool or relative to the
restraining mechanism.
[0208] The tool may further comprise a shearing mechanism.
[0209] The shearing mechanism may be a mechanical shearing
mechanism.
[0210] The shearing mechanism may be configured to be driven by
propellant combustion gases.
[0211] The shearing mechanism may be configured to act at or next
to the location where combustion jet(s) are directed.
[0212] The shearing mechanism may contain, enclose or encompass a
portion of the propellant source.
[0213] A portion of same propellant, which drives the mechanical
shearing mechanism, may also be directed at the target.
[0214] The shearing mechanism may comprise a shearing
mechanism.
[0215] The tool may be configured to sever the target by the
cooperative action of the propellant combustion jet(s) and the
shearing mechanism. In at least one embodiment of the present
invention a portion of the target is removed by the propellant
combustion jets while the remainder is severed or removed with the
shearing mechanism. In another embodiment, a portion of the target
is heated by the propellant combustion jet(s), allowing the
shearing mechanism to more easily sever or otherwise interact with
the target.
[0216] According to a fourth aspect of the present invention there
is provided a severance tool for severing a target, the severance
tool comprising:
[0217] a housing;
[0218] at least one propellant source;
[0219] a plurality of nozzles;
[0220] a nozzle holder adapted, in use, to encircle the target to
be severed, the nozzle holder being adapted to hold the
nozzles;
[0221] a trigger mechanism adapted to activate the/each propellant
source; and
[0222] a centralising means adapted, in use, to create relative
movement between the target and the nozzle holder to centralise the
target with respect to the nozzle holder.
[0223] It will be understood that the preferred and alternative
features listed in connection with one aspect of the invention may
be equally applicable to another aspect but have not been included
for brevity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0224] Embodiments of the present invention will now be described
with reference to the accompanying drawings in which:
[0225] FIG. 1 is, a schematic of an oilwell incorporating a tool
for severing or assisting in the severing of a conduit according to
a first embodiment of the present invention;
[0226] FIG. 2 is a section of the tool of FIG. 1;
[0227] FIGS. 3 to 5 are sections of the tool of FIG. 1 in
operation;
[0228] FIG. 6 is a section of a tool for severing or assisting in
the severing of a conduit according to a second embodiment of the
present invention
[0229] FIGS. 7 and 8 are sections of part of the tool of FIG. 6 in
operation;
[0230] FIG. 9 is a section of a tool for severing or assisting in
the severing of a conduit according to a third embodiment of the
present invention; and
[0231] FIGS. 10 to 13 are sections of part of the tool of FIG. 9 in
operation.
DETAILED DESCRIPTION OF THE DRAWINGS
[0232] Reference is first made to FIG. 1, a schematic of an oil
well generally indicated by reference numeral 5, incorporating a
tool 10 for severing or assisting in the severing of a conduit 12
according to a first embodiment of the present invention.
[0233] The tool 10 is part of a well string 14 providing fluid
communication between a reservoir 16 and a rig 18. The primary
components of the conduit 14 are a riser 20, the tool 10 and a
wellbore 22 lined with a casing 24.
[0234] The rig 18 floats on the sea 26 and receives hydrocarbons
from the reservoir 16 which flow into the well string 14, as
indicated by the arrow 28, and particularly into the conduit 12,
towards surface.
[0235] Referring now to FIG. 2, a section of the tool 10, the tool
10 is an integral part of the blowout preventer (BOP) and comprises
a housing 30 defining a void 32. The void 32 is a through bore 34
fully encircling the conduit 12. Located within the housing 30 is a
first propellant source 36 and a second propellant source 38.
[0236] A housing internal wall 40 defines a first circumferential
void access 42 having an inlet 44 in fluid communication with a
housing interior 46 and an outlet 48 in fluid communication with
the through bore 34. Similarly the housing internal wall 40 defines
a second circumferential void access 50 with an inlet 52 and an
outlet 54, the second circumferential void access 50 providing
fluid communication between the housing interior 46 and the through
bore 34.
[0237] The tool 10 further comprises a first shear ram 58 and a
second shear ram 60, the purpose of which will be discussed in due
course, and an ignition mechanism 56 for igniting the first and
second propellant sources, 36, 38.
[0238] The tool 10 is activated in a well control emergency in
which it is necessary to seal the wellbore 22 by closing the shear
rams 58, 60. This requires severance of the conduit 12.
[0239] The propellant sources 36, 38 are potassium perchlorate.
Upon ignition by the ignition mechanism 56, the propellant sources
36, 38 deflagrate, forming a hot gas of combustion products which,
due to the confines of the housing 12, is highly pressurised. The
propellant sources 36,38 further comprise a modifying material in
the form of a metal, in this case silver (not visible) embedded in
the potassium perchlorate. The deflagration process heats the
silver until the silver becomes molten.
[0240] The highly pressurised combustion products produced by the
deflagration of the potassium perchlorate flows away from the
propellant sources 36, 38 at great velocity as a stream of
combustion products carrying with it the molten silver modifying
material.
[0241] The streams of combustion gases carrying the molten silver
modifying material can be seen with reference to FIG. 3, a section
of the tool 10 showing the beginning of the process of severing a
conduit 12.
[0242] The propellant sources 36, 38 have been ignited by the
ignition mechanism 56 and the propellant sources 36, 38 have
released a first stream and a second stream of combustion products
62, 64 containing the molten silver modifying material.
[0243] The streams of combustion products 62, 64 flow towards, and
impinge on, the housing internal wall 40. Part of the streams of
combustion products, 62, 64 flow through the first and second
circumferential void accesses 42, 50 and impact on the conduit
12.
[0244] The gas within the streams of combustion products 62, 64
heat the conduit 12 and the modifying material melts the conduit
12. As the conduit melts, the streams of combustion products 62,64
move the molten material away revealing and further melting conduit
material. Through this process, conduit 12 is severed or at the
very least softened by the streams of combustion products 62, 64
containing the modifying material in the form of molten silver.
[0245] As shown in FIG. 4, the streams of combustion products 62,
64 containing the molten silver modifying material, work through
the conduit 12 until, as shown in FIG. 5 the first and second
propellant sources 36, 38 have been fully deflagrated, the conduit
12 has been severed and the shear rams 58, 60 can close sealing the
through bore 34.
[0246] Reference is now made to FIG. 6, a section of one side of a
tool 110 according to a second embodiment of the present
invention.
[0247] The tool 110 is similar in many ways to the tool 10 of the
first embodiment and rather than repeat the structural
similarities, the primary differences will be highlighted.
[0248] The tool 110 has a single circumferential void access 142
defined by the housing internal wall 140. The circumferential void
access 142 has a seal sleeve 166 covering the circumferential void
access 142 to prevent ingress of well fluids from the through bore
134 into the housing interior 146.
[0249] There are three propellant sources 168, 170, 172 shown in
FIG. 6. The upper and lower sources 168, 172 produce a gas, the
purpose of which will be discussed in due course. The middle
propellant source 170 is of similar construction to the propellants
36, 38 of the first embodiment, and produces a similar effect.
[0250] The tool 110 further comprises a positioning mechanism 173
in the form of a plurality of arms, of which one is visible in FIG.
6. These arms are pressed against the conduit 112 to bring the
conduit into the optimum position for severance.
[0251] The operation of the tool 110 will now be described. To give
the propellant 170 the best environment in which to sever the
conduit 112, it is it is desirable to remove any well fluids in the
through bore 134.
[0252] Referring to FIG. 7, the conduit has been positioned in the
optimum position with respect to the tool 110 by the positioning
mechanism 173. Once positioned, the upper and lower gas producing
propellant sources 168, 172 are ignited by the ignition mechanism
(not visible) creating a flow of high pressure combustion gas 174.
This pressurises the seal sleeve 166 (not shown in FIG. 7) until
the seal sleeve 166 ruptures and the gas 174 escapes through the
void access 142 into the through bore 134, driving well fluids away
from the propellant source stream of combustion products and
modifying material (shown in FIG. 8).
[0253] Referring to FIG. 8, a potassium perchlorate propellant 170
is then ignited by an ignition mechanism (not visible) and a stream
of combustion products carrying a modifying material 164, in this
case garnet, flows towards the conduit 112. The high pressure
combustion gas 174 formed from the deflagration of the upper and
lower gas producing propellant sources 168, 172 channels the stream
of combustion products 164 towards the target. On impact with the
conduit 112, the garnet modifying material is in solid form and
removes material from the conduit 112 by abrasion.
[0254] The use of the combustion gas 174 reduces friction between
the stream of combustion products carrying a modifying material 164
and the housing wall 140 around the void access 142. This maximises
the energy of the stream of combustion products 164, thereby
increasing the efficiency of the severing of the conduit 112.
[0255] FIG. 9 shows a third embodiment of a tool 210 for severing
through a conduit 212. In this case the tool 210 is fitted to the
outside of a tubular 276 through which the conduit 212 passes. The
conduit 212 has an increased diameter portion 278 which, in
essence, is a non-shearable object in that the increased diameter
portion 278 is too thick for a conventional BOP to sever using
conventional shear rams.
[0256] The tool 210 utilises three potassium perchlorate propellant
sources 268, 270, 272, each propellant source being associated with
a void access 280, 282, 284, each void access 280, 282, 284 being
arranged to channel a stream of combustion products and a molten
silver modifying material (not shown in this Figure but discussed
in due course) towards a different focal point, progressively an
increasing distance away from the tool 210.
[0257] The tool 210 further comprises an ignition mechanism 238 and
a first and second barrier 286, 288. The barriers 286, 288 prevent
one propellant source 268, 270, 272 igniting an adjacent propellant
source 268, 270, 272 as will be shown.
[0258] The operation of the tool 210 will now be described with
reference to FIG. 10.
[0259] As shown in FIG. 10, the first propellant source 270 has
been ignited by the ignition mechanism 238 and a first stream of
combustion products and modifying material 290 flows through the
first void access 280, first piercing the tubular 276 and then
moving material from the conduit increased diameter portion
278.
[0260] Referring to FIG. 11, the first propellant source 270 has
completed deflagration and the flame transfers up a first fuse 292
inside the second barrier 288 to the second propellant source 272
which deflagrates producing a second stream of combustion products
and modifying material 294 which flows through the second void
access 282, first piercing the tubular 276 and then moving material
from the conduit increased diameter portion 278. It will be noted
that the focal point of this second stream of combustion products
and modifying material 294 is deeper into the conduit increased
diameter portion 278.
[0261] Referring to FIG. 12, the second propellant source 272 has
completed deflagration and the flame transfers up a second fuse 296
inside the ignition mechanism 238 to the third propellant source
268 which deflagrates producing a third stream of combustion
products and modifying material 298 which flows through the third
void access 284, first piercing the tubular 276 and then moving
material from the conduit increased diameter portion 278. It will
be noted that the focal point of this third stream of combustion
products and modifying material 298 is deeper again into the
conduit increased diameter portion 278.
[0262] Finally referring to FIG. 13, upon completion of the
deflagration of the third propellant source 268, the conduit 212 is
severed.
[0263] Various modifications and improvements may be made to the
above described embodiments without departing from the scope of the
invention. For example, although the tool is described integrated
into a blow out preventer (BOP), to form an integral part of the
BOP, the tool may be positioned adjacent a BOP. In other
embodiments it can be used with other suitable well control
equipment, for example a rigless/riserless well intervention system
or in other locations such as with a riser or as part of a downhole
completion.
[0264] When used with a riser, the tool may form an integral part
of the riser. In some embodiments the tool may sever the riser
itself in an emergency, including all the control lines and other
equipment items. For this functionality it may also include a
sealing mechanism to seal off the riser itself and prevent a spill
of the fluids in the riser to sea.
[0265] Similarly, when integrated into a downhole completion to
form an integral part of the downhole completion the tool may also
include a sealing mechanism to seal off the well itself to prevent
fluids travelling up the wellbore to surface.
[0266] In all of these locations the tool may act as the primary
method for severing shearable and/or non-shearable items that may
be passing through the tool void.
* * * * *